Basically, you will no longer need to install the BP Template Pack plugin to make your WP theme compatible with BuddyPress as this new feature serves as a fallback for any WP theme which does not have BuddyPress templates in it. The feature is the same way bbPress plugin templates are served up in WP themes.

== why buddypress doesn’t use user_metadata and have a proprietary xprofile table. ==

I believe one reason would be that WP doesn’t have an API for BuddyPress’ more sophisticated profile fields/groups, or something of that nature. At least that’s what I recall a core dev answering the last time that question was asked

Paul, anyway it’s pretty simple to use both methods. We know that default wp_users support first_name, last_name, nickname and description (bio). Maybe you could make possibile to modify each of that from buddypress (i made it in my theme) and make a base group with these fields. Then if administrators want to add more fields and groups you could populate xprofile table. In this way you could have a more deep integration into WordPress.